Whenever a move my mouse, my FPS drastically drops, making the game unplayable as I can't aim at all. I've tried lowering the graphics settings, but that doesn't work. How can I fix this?

Make sure that you've removed all plugins and verifiy this is still happening.

That's bizarre. I think the obvious question is is this recent or has it always been? And what changed between when it worked and when it didn't? Basic troubleshooting.

It's like a few weeks ago. Maybe something to do with an update? And I haven't installed any plugins since then, so yeah. However, I will try de-installing targetless, see if that helps.

It could also be some software that came with your mouse. Do you have any extra drivers or "game panel" things installed?

Nope.

Remove all your plugins, not just one. Just because a plugin hasn't changed, doesn't mean the game hasn't broken it, or made it very slow.

If it still happens with NO PLUGINS INSTALLED at all, then it's the game's bug.
If it doesn't, then it's likely a plugin, a matter of trial and error to find which one. In this case, it's up to the plugin developer or any coders to fix it.

Try to fly so you don't have to move the mouse as much. Your mouse movement should be minimal, and your evasive maneuvers should bring them into your sights. Just think of this as incentive.

^ This actually makes you *really* easy to hit with flares. If your enemy catches on, they can use the leadoff to strafe you into a good position.

There are techniques to minimize this, but you are right if people don't change up their strafes/rolls, or roll more than 25% in any given direction.